Generally, there are a type of medicaments that can be stored for a long time and that are filled in containers as e.g. cartridges, syringes, ampoules, canisters or the like, containing a ready-to-use medicament in liquid state. There are also other type of medicaments that are a mixture of a medicament agent (e.g. lyophilized, powdered or concentrated liquid) and a diluent (e.g. water, dextrox solution or saline solution), wherein these type of medicaments can not be pre-mixed and stored for a long time because the medicament agent is unstable and can be degraded and loses its effect quickly. Hence, a user, e.g. a patient himself/herself, a physician, a nurse, hospital personnel or trained persons, has/have to perform the mixing within a limited time period prior to the delivery of a dose of medicament to a patient. Further, some medicament agents are subject to meet significant chemical changes while mixing. Such sensitive medicament agents require a particular treatment so that, when mixing said medicament agents with a diluent, unreasonable mixing force will degrade said medicament agents.
In order to facilitate the mixing, a number of containers for mixing have been developed comprising at least two chambers, a multi-chamber container, one chamber containing the medicament agent and the other chamber containing the diluent. Said chambers are sealed off with plungers in order that the medicament agents do not become degraded. When the medicament agent is to be mixed, e.g. passages are opened between the chambers, usually by depressing a rear plunger and in turn a divider plunger of the container somewhat. The passages allow the mixing of the medicament agent and the diluent and the medicament is ready for delivery.
Multi-chamber containers usually contain a lot of air/gas, especially when the medicament agent is in powder form, which air/gas is present when the medicament agent and the diluent are mixed. This entrapped air/gas is often desirable to get removed, priming, before delivery.
The above mentioned requirements can be achieved by simple medicament delivery devices, such as a common hypodermic syringe, but the procedure is of course rather awkward, in particular for persons not used to handle these devices. In order to facilitate for the patient themselves to administer the medicament with a predetermined dose in an easy, safe and reliable way and also to facilitate the administration of medicaments for hospital personnel in the same facilitated way, a number of automatic and semi-automatic devices have been developed in combination with these multiple-chamber solutions for obtaining a mixing before delivery.
A self-injection device arranged with a dual-chamber container, wherein both the mixing and the injection are done automatically by mechanical means, as springs and other means, is disclosed in U.S. Pat. No. 4,755,169.
A similar solution is disclosed in U.S. Pat. No. 6,793,646 wherein the mixing of a dual-chamber cartridge is done is done automatically by springs upon activation of the device and the injection is done by manually applying a force to a plunger rod forwardly.
A drawback with these devices is that the mixing force, to which medicament agents are subject to, is too high at the beginning due to Hookes law. Hence, the medicament agents can be degraded. Further, such devices can be primed holding them at different positions, which do not ensure that the air or gas entrapped in the container is expelled.
Another solution is disclosed in WO 2004004809, wherein both the mixing and the injection are done automatically by electronics controlled means. A drawback with this device is that the electronics are dependent on batteries and is very sensitive to noise, moisture, water, etc.; which can result in malfunctions. Even more the manufacture of these devices is more expensive than the manufacture of mechanical devices.
In U.S. Pat. No. 6,893,420 is disclosed a self-injection device arranged with a dual-chamber body. The penetration and injection is done automatically upon activation of the device and the mixing is done manually by a screw-tightening operation of a rear cap, whereby a plunger rod applies a force on a plunger inside the dual-chamber body such that a mixing is obtained. A drawback with this device is that users having impaired manual dexterity have difficulties in handling such a device.
Another similar solution is disclosed in U.S. Pat. No. 6,319,225 where the mixing of a dual-chamber ampoule is done by manually. The device is set to be vertical on a flat plane and then a downward press on its front case causes a relative upward movement of its plunger rod pressing a plunger of the ampoule with eye observation on actions inside the ampoule, such that a mixing is obtained. Though in U.S. Pat. No. 6,319,225 is disclosed that the best suitable process for mixing a medicament agent with a diluent, is by performing manual control of the diluent flow with adequate slowness which will be monitored by eye observation.
A drawback with the above mentioned devices is that the mixing force, to which medicament agents are subject to, can be high if the user is stressed and wants to use the device as soon as possible or. Hence, the medicament agents can be degraded. Further, the device disclosed in U.S. Pat. No. 6,893,420 can be primed holding it at different positions, which does not ensure that the air or gas entrapped in the container is expelled.
Heretofore, a number of devices have been disclosed for pre-treating, e.g. mixing a medicament agent and a diluent and priming, multi-chambered containers before the delivery of a dose of medicament to a patient; but such devices admit of further improvements in view of pre-treating multi-chambered containers for preventing a too high mixing force degrading the medicament agents and priming in a correct and safe way.